Colloidal suspension of submicronic particles for carrying active principles and their mode of preparation

ABSTRACT

The invention concerns a suspension of biocompatible particles for carrying active principles. Said carrier particles are based on a double-block hydrophilic neutral polyaminoacid/hydrophobic neutral polyaminoacid copolymer. Said hydrophilic neutral polyaminoacid/hydrophobic neutral polyaminoacid particles are capable of combining in colloidal suspension in non-dissolved state, at least an active principle and of releasing same, in particular in vivo, in prolonged and/or delayed delivery. The invention also concerns a powdery solid from which are derived the carrier particles and the preparation of said solid and of said suspension of active principle based on hydrophilic neutral polyaminoacids/hydrophobic neutral polyaminoacids. Said carrier particles form spontaneously and in the absence of surfactants or organic solvents, stable aqueous suspensions. The invention also concerns the carrier particles in dry form, the method for preparing them, and pharmaceutical compositions (in dry form or suspension) comprising said carrier particles associated with an active principle.

TECHNICAL FIELD

The present invention relates to the field of carrier particles (CP) that are useful for the administration of active principles (AP). The latter are preferably drugs or nutriments for administration to an animal or human organism by the oral or nasal, vaginal, ocular, subcutaneous, intravenous, intramuscular, intradermal, intra-peritoneal, intracerebral, parenteral or other route. However, they can also be cosmetic products or plant health products such as herbicides, pesticides, insecticides, fungicides, etc. In terms of their chemical nature, the AP to which the invention relates more particularly, but without implying a limitation, are e.g. proteins, glycoproteins, peptides, polysaccharides, lipopolysaccharides, oligo-nucleotides, polynucleotides and organic molecules.

The present invention relates more precisely to colloidal suspensions of carrier particles, advantageously of the submicron type, that are based on polyamino acids (PAA).

The present invention relates both to bare particles as such, and to AP carrier systems consisting of the particles loaded with the AP in question.

The present invention further relates to pulverulent solids comprising these CP.

The invention further relates to methods of preparing said colloidal suspensions of particles, with or without AP.

PRIOR ART

The purpose of encapsulating or adsorbing AP in CP is especially to modify their duration of action and/or convey them to the treatment site and/or increase the bioavailability of said AP. Numerous encapsulation techniques have already been proposed. The aim of such techniques is on the one hand to enable the AP to be transported to its site of therapeutic action while at the same time protecting it from the aggressions of the organism (hydrolysis, enzymatic digestion, etc.), and on the other hand to control the release of the AP at its site of action so that the amount available to the organism is maintained at the desired level. The AP involved in these changes in transport and residence in the organism are e.g. proteins, but they can also be products that are quite different from organic molecules of synthetic or natural origin. The review by M. J. HUMPHREY (Delivery system for peptide drugs, edited by S. DAVIS and L. ILLUM, Plenum Press, N.Y. 1986) discusses the problem associated with the improvement of AP bioavailability and the advantage of carrier and controlled release systems.

The CP according to the invention are of the type on which the AP is adsorbed.

Of all the materials that can be considered for forming CP, polymers are increasingly widely used because of their intrinsic properties. The specifications sheet which it is desired to obtain for the CP is particularly demanding and comprises the following specifications in particular:

-   -   1 The first specification sought for the CP would be that the         polymer constituting the CP is biocompatible, capable of         elimination (by excretion) and/or biodegradable, and         particularly that it is metabolized to products that are         non-toxic to the organism. In addition, the biodegradation in         the organism should be of a sufficiently short duration.     -   2 It would be advantageous for the CP to be able to form a         stable aqueous suspension without the aid of an organic solvent         and/or a surfactant.     -   3 It would also be desirable for the CP to be sufficiently small         to be able to undergo, in suspension in a liquid, a sterilizing         filtration with a filter whose pore diameter is less than or         equal to 0.2 μm.     -   4 It is desirable for the CP and the CP-AP systems to be         obtainable by a method that is non-denaturing towards the AP.     -   5 The CP should advantageously make it possible to control the         rate of release of the AP.     -   6 Another important specification would be for the CP-AP systems         to be able to constitute excellent injectable drugs. This         improved suitability for administration by injection—e.g.         intravenous or intramuscular injection—or “injectability” is         characterized by:         -   (i) a reduced injected volume (for a given therapeutic             dose), and         -   (ii) a low viscosity.         -   These two properties are satisfied when the therapeutic dose             of AP is associated with a minimum amount of CP. In other             words the CP must have a high AP loading factor.     -   7 The inherent cost of the CP in an injectable preparation must         be reduced and, here again, the CP should have a high AP loading         factor. In fact, the small size and high loading factor are         major specifications sought for the CP.     -   8 It is also advantageous if the constituent polymer of the CP         does not induce an immune response.

The earlier technical proposals, described below, attempted to meet all these specifications. The earlier proposals (a) to (h) will be mentioned by way of illustration:

-   -   (a) U.S. Pat. No. 5,286,495 relates to a method of encapsulation         by the vaporization of proteins in the aqueous phase with the         aid of materials carrying opposite charges, namely alginate         (negatively charged) and polylysine (positively charged). This         manufacturing process makes it possible to produce particles         with a size above 35 μm.     -   (b) Furthermore, emulsion techniques are commonly used to         prepare microparticles loaded with AP. For example, patent         applications WO 91/06286, WO 91/06287 and WO 89/08449 disclose         such emulsion techniques in which organic solvents are used to         solubilize polymers, for example of the polylactic type.         However, it has been found that the solvents can be denaturing,         especially for peptide or polypeptide AP.     -   (c) Biocompatible CP called proteinoids are also known, having         been described since 1970 by X. FOX and K. DOSE in “Molecular         evolution and the origin of life”, published by Marcel DEKKER         Inc. (1977). Thus patent application WO 88/01213 proposes a         system based on a mixture of synthetic polypeptides whose         solubility depends on the pH. To obtain the matrix         microparticles according to said invention, the authors         solubilize the mixture of polypeptides and then, with a pH         change, they cause proteinoid particles to precipitate. When the         precipitation takes place in the presence of an AP, the latter         is encapsulated in the particle.     -   (d) U.S. Pat. No. 4,351,337, which relates to a different field         from that of AP transport peculiar to the present invention, may         also be cited as a matter of interest. Said patent discloses         mass implants fixed and localized in very specific places in the         organism. These implants are tubes or hollow capsules of         microscopic size (160 μm, with a length of 2000 μm) which         consist of polyamino acid copolymers—e.g. poly(glutamic         acid/leucine) or poly(benzyl glutamate/leucine)         copolymers—obtained by the copolymerization of amino acid         N-carboxy anhydride (NCA) monomers. An AP is included by a         technique of solvent evaporation from a mixture of polymer and         AP. U.S. Pat. No. 4,450,150 belongs to the same family as U.S.         Pat. No. 4,351,337 studied above, and has essentially the same         subject matter. The constituent PAA are poly(glutamic acid/ethyl         glutamate) copolymers.     -   (e) Patent application EP 0 734 720 relates to polyamino acid         particles that are useful for carrying AP. These particles have         a size of between 10 and 500 nm, preferably of between 30 and         400 nm.         -   The particles according to EP 0 734 720 are formed             spontaneously when PAA are brought into contact with an             aqueous solution. The PAA include hydrophobic neutral amino             acid monomers, AANO (Leu, Ile, Val, Ala, Pro, Phe), and             hydrophilic ionizable monomers, AAI (Glu, Asp). These PAA             are prepared by copolymerizing NCA of AAI precursors (e.g.             Glu-OMe) and NCA of AAO (e.g. Leu) in solution in a             dioxane/toluene mixture. The poly(Glu-OMe/Leu) copolymer             obtained in solution is recovered by precipitation in water,             filtration and drying. This copolymer is then subjected to             acid hydrolysis by being incorporated into trifluoroacetic             acid         -   (TFA), in which it dissolves. A poly(Glu-O-Na/Leu) copolymer             is recovered after neutralization, dialysis, filtration and             lyophilization. The coPAA is dispersed in an aqueous             solution of NaCl and a suspension of nanoparticles forms             spontaneously. As soon as these CP in aqueous suspension are             brought into contact with an AP, the latter associates             spontaneously with the CP by adsorption. The CP have a             hydrophobic core formed of hydrophobic amino acids and a             hydrophilic external “lattice” based on hydrophilic amino             acids.         -   It is pointed out that the carrier particles according to EP             0 734 720 contain ionizable amino acids (Glu) carrying a             negative stabilizing electric charge, making it possible to             prevent the particles, CP, from flocculating and             aggregating.     -   (f) FR-A-2 746 035 relates to microparticles of composite gel         that are physicochemically stable, integral and capable of being         used as active principle carriers. These microparticles consist         of oil (I), aqueous phase (II) and at least one linear,         non-crosslinked, synthetic copolyamino acid (III) containing at         least two different types of amino acid comonomers: hydrophilic,         AAI, and hydrophobic, AAO. The AAI can be Glu, Asp, Orn, Arg,         Lys, Asn, His and associations thereof. The AAO comonomers can         be Leu, Tyr, Phe, Val, Cys, Ile and associations thereof. On         page 27, lines 8 to 18, in particular, FR-A-2 746 035 describes         an aqueous colloidal suspension of polyamino acids, for example         poly(leucine/sodium glutamate) copolymer.

However, FR-A-2 746 035 does not disclose the use of the copolymers by themselves as a nanoparticulate pharmaceutical system for carrying AP.

The AAI of FR-A-2 746 035 are not hydrophilic neutral amino acids selected from the group comprising:

-   -   the following natural neutral amino acids: serine, threonine,         hydroxyproline, glutamine;     -   the following rare or synthetic neutral amino acids: methionine         S-oxide, O-glycosidylserine; and     -   the following derivatives of neutral amino acids:         N-hydroxyethyl-glutamine, N-hydroxypropylasparagine.

All these earlier technical proposals described above:

-   -   either incompletely meet the specifications of the         specifications sheet indicated above, particularly as regards         suitability for sterilization by filtration, high degradation         rate, adaptability to the constraints of drug administration by         injection, low cost and high AP loading factor;     -   or could be replaced by novel technical solutions capable of         affording novel advantages (prior art reference EP 0 734 720).

BRIEF DISCLOSURE OF THE INVENTION

With these facts established, one essential objective is to be able to provide novel CP which form stable aqueous suspensions of CP spontaneously, without the aid of surfactants or organic solvents.

Another essential objective of the present invention is to provide novel CP in stable colloidal aqueous suspension or in pulverulent form, based on polyamino acids (PAA), these novel CP preferably meeting specifications 1 to 8 of the specifications sheet mentioned above.

Another essential objective of the invention is to improve the particles disclosed in PCT patent application WO 96/29991.

Another essential objective of the invention is to provide a novel suspension of CP whose characteristics are perfectly controlled, especially in terms of the AP loading factor and in terms of control of the AP release kinetics.

Another essential objective of the invention is to provide injectable medicinal suspensions. The specifications required for such suspensions are a small injection volume and a low viscosity. It is important that the mass of colloidal particles per injection dose be as small as possible, without limiting the amount of active principle, AP, transported by these particles, so as not to detract from the therapeutic efficacy.

Another essential objective of the invention is to provide a colloidal aqueous suspension or a pulverulent solid which comprises active principle carrier particles meeting the above-mentioned specifications, and which constitutes an appropriate galenical form suitable for administration, for example orally, to humans or animals.

Another essential objective of the invention is to provide a colloidal suspension comprising active principle carrier particles that can be filtered on 0.2 μm filters for sterilization purposes.

Another essential objective of the invention is to propose a method of preparing PAA particles (dry or in suspension in a liquid) that are useful especially as active principle carriers, said method being simpler to carry out and non-denaturing towards the active principles and additionally always allowing fine control over the mean size of the particles obtained.

Another essential objective of the invention is to use the above-mentioned particles, in aqueous suspension or in solid form, for the preparation of

-   -   drugs (e.g. vaccines), especially for oral, nasal, vaginal,         ocular, subcutaneous, intravenous, intramuscular, intradermal,         intraperitoneal, intracerebral or parenteral administration, it         being possible in particular for the active principles of these         drugs to be proteins, glycoproteins, peptides, polysaccharides,         lipopolysaccharides, oligonucleotides and polynucleotides;     -   and/or nutriments;     -   and/or cosmetic or plant health products;     -   and/or medicinal organic molecules.

Another essential objective of the present invention is to provide suspensions of submicron CP based on PAA that are capable of acting as a carrier for an AP, particularly a medicinal AP for administration to a human or animal organism, or alternatively a nutritional, plant health or cosmetic AP.

Another objective of the present invention is to provide a drug, of the type consisting of a system for the prolonged release of active principles, which is easy and economic to produce and which is also biocompatible and capable of assuring a very high level of bioavailability of the AP.

Another essential objective of the invention is to provide a vaccine carrier system which is non-immunogenic intrinsically and in combination with one or more antigens.

The product-related objectives (among others) are achieved by the present invention, which relates first and foremost to a stable colloidal suspension of submicron structured particles capable of being used especially for carrying one or more active principles, AP, these particles being individualized (discrete) supramolecular arrangements that are:

-   -   based on linear amphiphilic polyamino acids (PAA) having peptide         linkages and comprising at least two different types of         hydrophilic repeating amino acids, AAI, and hydrophobic         repeating amino acids, AAO, the amino acids of each type being         identical to or different from one another;     -   capable of associating at least one AP in colloidal suspension,         in the undissolved state, and releasing it, especially in vivo,         in a prolonged and/or delayed manner;     -   and stable in the aqueous phase at a pH of between 4 and 13, in         the absence of surfactant(s), characterized:         -   in that the hydrophilic repeating amino acids, AAI, are             hydrophilic neutral amino acids, AANI, with the exclusion of             asparagine;         -   in that the hydrophobic repeating amino acids, AAO, are             hydrophobic neutral amino acids, AANO;         -   and in that the repeating amino acids of each type, AANI and             AANO, are identical to or different from one another.

DETAILED DISCLOSURE OF THE INVENTION

One of the main inventive aspects of these novel carrier particles, CP, in stable colloidal aqueous suspension or in the form of a pulverulent solid, concerns the novel selection of a group of polymers and a novel methodology for obtaining particles of submicron size which form a stable colloidal aqueous suspension in the absence of surfactants or solvents.

Another main inventive aspect of these novel carrier particles, CP, in stable colloidal aqueous suspension or in the form of a pulverulent solid, concerns the novel selection of two neutral amino acids as hydrophilic repeating monomers, AANI, and hydrophobic repeating monomers, AANO.

Now, contrary to what those skilled in the art might have feared, not having ionizable hydrophilic amino acids, AAII, i.e. negative charges, as in the particles according to WO 96/29991, does not detract from the stability. In fact, contrary to all expectations, the colloidal suspension according to the present invention does not flocculate. The particles based on-poly(AANI/AANO) do not self-aggregate. Moreover, it was not at all obvious a priori that these particles of poly(AANI/AANO) would be capable of associating spontaneously with active principles, AP, and releasing these AP at the sites of therapeutic action.

The structure of the PAA polymers and the nature of the neutral amino acids are chosen so that:

-   -   the polymer chains spontaneously organize themselves into small         particles (CP);     -   the particles form a stable colloidal suspension in water and in         a physiological medium;     -   the CP associate with proteins or other AP in aqueous media by a         spontaneous mechanism that is non-denaturing towards the         protein; and     -   the CP release the AP in a physiological medium and, more         precisely, in vivo; the release kinetics depend on the nature of         the PAA polymer that is the CP precursor.

Thus, by varying the specific structure of the PAA, it is possible to control the AP association and release phenomena from the kinetic and quantitative points of view.

It is to the Applicant's credit to have chosen, as the constituent material of the CP, a specific composition of neutral polyamino acids which are amphiphilic and therefore possess properties of CP made of PAA, namely:

-   -   the possibility of spontaneously forming colloidal suspensions         of CP that are compatible with the pH of the physiological media         encountered in the intended therapeutic applications;     -   spontaneous association of the AP with CP in the absence of any         agent other than water, which acts as solvent and, in the case         of proteins, is non-denaturing;     -   the possibility of releasing the AP from the AP-CP association         complex under physiological conditions with pharmacokinetic and         pharmaco-dynamic profiles which lead to the expectation of         valuable uses in the therapeutic field (AP transport);     -   filterability with a cut-off threshold less than or equal to 0.2         μm for sterilization purposes;     -   improved biodegradability; and     -   optimized injectability.

These PAA can be of the ordered type with alternate sequences (blocks) or of the disordered type with random sequences.

Thus, in a first embodiment of the CP according to the invention, the constituent PAA are of the “block” type and are characterized by a molar ratio AANO/(AANI+AANO) which is such that:

-   -   AANO/(AANI+AANO)≧6%,     -   10%≦AANO/(AANO+AANI)≦70%,     -   preferably, 20%≦AANO/(AANI+AANO)≦60%,     -   and particularly preferably, 35%≦AANO/(AANI+AANO)≦50%.

Advantageously, the absolute length of each block of AANO, expressed as the number of AANO, is such that:

-   -   AANO≧5,     -   preferably, AANO≧10,     -   and particularly preferably, AANO≧20.

In a second embodiment of the CP according to the invention, the constituent PAA are of the “random” type, i.e. prepared by the simultaneous copolymerization of AANI and AANO monomers, and the molar ratio AANO/(AANO+AANI) is such that:

-   -   AANO/(AANO+AANI)≧10%,     -   preferably, AANO/(AANO+AANI)≧20%,     -   and particularly preferably, 30%≦AANO/(AANI+AANO)≦70%.

Advantageously, the molecular weight, Mw, of these random PAA is such that:

-   -   Mw≧2000 g/mol,     -   preferably, Mw≧5500 g/mol,     -   and particularly preferably, 5500 g/mol≦Mw≦200,000 g/mol.

According to a preferred characteristic of the invention, the block or random PAA constituting the particles have degrees of polymerization, DP, of between 30 and 600, preferably of between 50 and 200 and particularly preferably of between 60 and 150.

Advantageously, the PAA constituting the particles, CP, are “di-block” PAA.

Preferably, the hydrophilic AANI is (are) selected from the group comprising:

-   -   natural neutral amino acids, preferably those selected from the         group comprising serine, threonine, hydroxyproline and         glutamine;     -   the rare or synthetic neutral amino acids, preferably those         selected from the group comprising methionine S-oxide and         O-glycosidylserine; and     -   derivatives of neutral amino acids, preferably those selected         from the group comprising N-hydroxyethylglutamine,         N-hydroxypropylasparagine, N-hydroxyethylasparagine and         N-hydroxypropylglutamine.

Advantageously, the hydrophobic AANO is (are) selected from the group comprising:

-   -   natural neutral amino acids, preferably those selected from the         group comprising Leu, Ile, Val, Ala, Pro and Phe;     -   rare or synthetic neutral amino acids, preferably those selected         from the group comprising norleucine and norvaline; and     -   derivatives of polar amino acids, preferably those selected from         the group comprising methyl glutamate, ethyl glutamate, benzyl         aspartate and N-acetyllysine.

According to an advantageous characteristic, the carrier particles (CP) of the suspension have a mean size of between 0.01 and 0.5 μm, preferably of between 0.01 and 0.2 μm.

Another preferred characteristic of the suspension is that it is aqueous and stable.

The present invention relates not only to suspensions of bare particles as defined above, but also to suspensions of particles comprising at least one active principle, AP. Preferably, the suspension according to the invention is aqueous and stable. These particles, whether loaded with AP or not, are advantageously in a form dispersed in a liquid (suspension), preferably an aqueous liquid, but can also be in the form of a pulverulent solid obtained from the suspension of CP as defined above.

It follows from this that the invention relates not only to a colloidal (preferably aqueous) suspension of CP, but also to a pulverulent solid comprising CP which is obtained from the suspension according to the invention.

Another essential object of the invention concerns the preparation of:

-   -   selected particles as described above;     -   and other selected particles which are structured, submicron and         capable of being used especially for carrying one or more active         principles, AP, these particles being individualized (discrete)         supramolecular arrangements that are:         -   based on linear amphiphilic polyamino acids (PAA) having             peptide linkages and comprising at least two different types             of hydrophilic repeating amino acids, AAI, and hydrophobic             repeating amino acids, AAO, the amino acids of each type             being identical to or different from one another;         -   capable of associating at least one AP in colloidal             suspension, in the undissolved state, and releasing it,             especially in vivo, in a prolonged and/or delayed manner;         -   and stable in the aqueous phase at a pH of between 4 and 13,             in the absence of surfactant(s), where:             -   the hydrophilic repeating amino acids, AAI, consist at                 least partly of asparagine;             -   and the hydrophobic repeating amino acids, AAO, are                 hydro-phobic neutral amino acids, AANO, which are                 identical to or different from one another,                 it being possible for these particles to be either in                 the form of a colloidal suspension or in the form of a                 pulverulent solid obtained from a stable colloidal                 suspension of particles.

The method of preparation in question consists essentially in synthesizing precursor PAA and converting them to structured particles.

More precisely, the method of preparation is first and foremost a method of preparing submicron structured particles capable of being used especially for carrying one or more active principles, these particles being discrete supramolecular arrangements that are:

-   -   based on linear amphiphilic polyamino acids (PAA) having peptide         linkages and comprising at least two different types of         hydrophilic repeating amino acids, AAI, and hydrophobic         repeating amino acids, AAO, the amino acids of each type being         identical to or different from one another;     -   capable of associating at least one AP in colloidal suspension,         in the undissolved state, and releasing it, especially in vivo,         in a prolonged and/or delayed manner;     -   and stable in the aqueous phase at a pH of between 4 and 13, in         the absence of surfactant(s).

This method is characterized in that:

-   -   1) a copolymerization is carried out between monomers formed of         amino acid N-carboxy anhydrides (NCA) of at least two different         types:         -   on the one hand starting NCA monomers comprising NCA-Glu-OR             and/or NCA-Asp-OR and/or NCA-AANI,         -   and on the other hand NCA-AANO, in the presence of:             -   at least one non-aromatic polar solvent preferably                 selected from the group comprising N-methylpyrrolidone                 (NMP), dimethylformamide (DMF), dimethyl sulfoxide                 (DMSO), dimethylacetamide (DMAc) and pyrrolidone, NMP                 being more particularly preferred;             -   and optionally at least one cosolvent selected from                 aprotic solvents (preferably 1,4-dioxane) and/or protic                 solvents (preferably pyrrolidone) and/or water and/or                 alcohols, methanol being particularly preferred;     -   2) in the case where the starting NCA monomers are NCA-Glu-OR         and/or NCA-Asp-OR(R=alkyl), an aminolysis is carried out which         consists in bringing the copolymer obtained in step 1 into         contact with an aqueous phase comprising at least one amine, and         which makes it possible to convert Glu-OR to Gln and Asp-OR to         Asn;     -   3) the reaction medium is optionally dialyzed to purify the         aqueous suspension of structured particles;     -   4) this suspension of step 3 is optionally concentrated; and     -   5) the liquid medium is removed so that the pulverulent solid         comprising the particles can be collected.

The first step of the method is based on the known techniques of polymerizing α-amino acid N-carboxy anhydrides (NCA), which are described for example in the article “Biopolymers, 15, 1869 (1976)” and in the work by H. R. KRICHELDORF entitled “α-Amino acid N-carboxy anhydride and related heterocycles”, Springer Verlag (1987).

Using carefully chosen polar, non-aromatic aprotic copolymerization solvents that avoid any precipitation, and using acid hydrolysis in the presence of water and a non-aromatic, polar organic solvent, affords submicron, discrete structured particles with a high AP loading capacity which form a stable colloidal suspension in aqueous media. These particles are in no way comparable to a macroscopic agglomerated precipitate of the kind referred to above in respect of earlier proposal (d).

In one variant, after step 1, the poly(AANO/AANI) copolymer obtained is precipitated—preferably in water—and this precipitate is collected. This variant corresponds to a batch mode of preparing particles in which the poly-(AANO/AANI) copolymer is isolated in the form of a precipitate constituting a stable intermediate. This precipitate can be filtered off, washed and dried, for example.

Particularly preferably, the NCA-pAAI are NCA of O-alkylated glutamic or aspartic acid, for example NCA-Glu-O-Me, NCA-Glu-O-Et or NCA-Glu-O-Bz (Me=methyl-Et=ethyl-Bz=benzyl).

In known manner, the copolymerization takes place at a temperature of between 20 and 120° C., at atmospheric pressure and in the presence of an amine initiator, e.g. NH₃.

Other experimental parameters, such as the concentration of NCA and/or polymer in the non-aromatic polar solvent (preferably NMP) and/or the concentration or nature of the protic cosolvent, during the synthesis, will be adjusted according to the desired effects known to those skilled in the art.

The acid hydrolysis (step 2) is carried out with water and at least one mineral acid such as phosphoric or hydrochloric acid—the latter being preferred—and/or at least one organic acid such as trifluoroacetic acid (TFA), acetic acid, dichloroacetic acid or organosulfonic acids.

The proportions of water/acid—expressed in parts by weight—in an acidic aqueous hydrolysis phase are advantageously:

-   -   from 60/1 to 2/1,     -   preferably 40/1 to 2/1,     -   and particularly preferably 20/1 to 2/1.

The proportions of acidic aqueous hydrolysis phase/NMP—expressed in parts by weight—are advantageously:

-   -   from 5/100 to 200/100,     -   preferably 10/100 to 100/100,     -   and particularly preferably from 20/100 to 80/100.

Other parameters, such as the polymer concentration, the temperature of the reaction mixture, the mode of addition of the acidic aqueous hydrolysis phase, the use of reduced pressure, the reaction time, etc., are adjusted according to the desired effects well known to those skilled in the art.

In practice, the neutralization (step 3) is carried out e.g. with sodium hydroxide. The salt formed at the end of the neutralization, and the solvent, are then removed by any appropriate physical separation treatment, for example by diafiltration (dialysis) (step 4), filtration, pH modification, chromatography, etc.

This yields an aqueous suspension of structured particles which can be concentrated, for example by distillation or any other suitable physical means such as ultrafiltration or centrifugation.

In step 6, to separate the particles from their liquid suspension medium, the aqueous phase is optionally removed, for example by drying (e.g. in an oven), lyophilization or any other suitable physical means such as ultrafiltration or centrifugation. A white pulverulent solid is recovered at the end of this step 6.

In one variant, the concentration step can be carried out by means of a chemical treatment, such as a lowering of the pH, which converts the hydrophilic part of the glutamate monomers to acid, making them insoluble in water. These acidic PAA intermediates can be filtered off, washed and dried. Said acidic intermediates can be neutralized with a chemical base in a subsequent step to give a suspension of particles.

It is pointed out that the implementation of steps 1, 2, 3, 4 and optionally 5 of the above method corresponds to a preparation of a colloidal suspension of submicron particles with a high AP loading factor.

In this preparation of a colloidal suspension, the amphiphilic PAA, poly(AANO/AANI), of step 2 are placed in an aqueous medium in which at least part of the AANI is soluble and at least part of the AANO is insoluble. The PAA exist in the form of nanoparticles in this aqueous medium.

An alternative preparation of the suspension of CP according to the invention consists in bringing the pulverulent solid, as described above as a product and by its method of preparation, into contact with an aqueous medium that is a non-solvent for the AANO.

One or more AP can be associated with the particles by using several methods according to the invention. Non-limiting examples of these methods are listed below.

According to a first method, an AP is associated with the particles by bringing a liquid phase (aqueous or non-aqueous) containing the AP into contact with the colloidal suspension of particles which may or may not comprise Asp as AANI.

According to a second method, the AP is associated with the particles by bringing an AP in the solid state into contact with the colloidal suspension of particles which may or may not comprise Asp as AANI. The solid AP can be e.g. in the form of a lyophilizate, precipitate or powder or in another form.

According to a third method, the pulverulent solid (PAA which may or may not comprise Asp as AANI), as described above as a product and by its preparative characteristics, is brought into contact with a liquid phase (aqueous or non-aqueous) containing the AP.

According to a fourth method, the pulverulent solid, as described above as a product and by its preparative characteristics (PAA which may or may not comprise Asp as AANI), is brought into contact with the AP in solid form. This mixture of solids is then dispersed in a liquid phase, preferably an aqueous solution.

In all these methods, the AP used can be in the pure form or a preformulated form.

Given the nanometric size of the particles, the suspension can be filtered on sterilization filters, enabling sterile injectable medicinal liquids to be obtained easily and at lower cost. The ability, afforded by the invention, to control the particle size and reach Dh values of between 25 and 100 nm is an important asset.

The present invention further relates to novel intermediates of the method described above, characterized in that they consist of PAA copolymers (which may or may not comprise Asp as AANI) that are particle precursors.

INDUSTRIAL APPLICATION

According to another of its features, the invention relates to a suspension and/or a pulverulent solid (PAA which may or may not comprise Asp as AANI) as defined above and/or as obtained by the method described above, this suspension and this solid comprising at least one active principle preferably selected from:

-   -   vaccines;     -   proteins and/or peptides, among which the following are more         preferably selected: hemoglobins, cytochromes, albumins,         interferons, antigens, antibodies, erythropoietin, insulin,         growth hormones, factors VIII and IX, interleukins or mixtures         thereof, and hemopoiesis-stimulating factors;     -   polysaccharides, heparin being more particularly selected;     -   nucleic acids and preferably RNA and/or DNA oligonucleotides;     -   non-peptido-protein molecules belonging to various anticancer         chemotherapy categories, particularly anthracyclines and         taxoids;     -   and mixtures thereof.

The invention further relates to a suspension and/or a pulverulent solid (PAA which may or may not comprise Asp as AANI) loaded with a nutritional, plant health or cosmetic AP.

Finally, the invention relates to a pharmaceutical, nutritional, plant health or cosmetic proprietary product, characterized in that it contains a suspension and/or pulverulent solid as defined above, loaded with AP.

According to another of its objects, the invention further relates to the use of these CP (in suspension or in solid form: PAA which may or may not comprise Asp as AANI), loaded with AP, for the manufacture of drugs of the type consisting of systems for the controlled release of AP.

In particular, the invention relates to the use of a stable colloidal suspension of submicron structured particles loaded with one or more active principles, AP, these particles being individualized (discrete) supramolecular arrangements that are:

-   -   based on linear amphiphilic polyamino acids (PAA) having peptide         linkages and comprising at least two different types of         hydrophilic repeating amino acids, AAI, and hydrophobic         repeating amino acids, AAO, the amino acids of each type being         identical to or different from one another;     -   capable of associating at least one AP in colloidal suspension,         in the undissolved state, and releasing it, especially in vivo,         in a prolonged and/or delayed manner;     -   and stable in the aqueous phase at a pH of between 4 and 13, in         the absence of surfactant(s), where:         -   the hydrophilic repeating amino acids, AAI, consist at least             partly of asparagine;         -   and the hydrophobic repeating amino acids, AAO, are             hydrophobic neutral amino acids, AANO, which are identical             to or different from one another,             for the preparation of an aqueous suspension or a             pulverulent solid as above defined, loaded with at least one             AP.

Examples of drugs are those that can preferably be administered by the oral, nasal, vaginal, ocular, subcutaneous, intravenous, intramuscular, intradermal, intra-peritoneal, intracerebral or parenteral route.

Examples of cosmetic applications that can be considered are compositions which comprise an AP associated with the CP according to the invention and which can be administered transdermally.

Examples of possible plant health products are herbicides, pesticides, insecticides, fungicides, etc.

The Examples which follow will provide a better understanding of the invention according to its different product/method/application features. These Examples illustrate the preparation of particles of polyamino acids which may or may not be loaded with active principles, and also present the structural characteristics and the properties of these particles.

EXAMPLES Example 1 Preparation of Poly(Leucine/Methyl Glutamate) Block Copolymer

The techniques used to polymerize NCA to polymers with block or random structures are known to those skilled in the art and are described in detail in the work by H. R. KRICHELDORF entitled “α-Amino acid N-carboxy anhydrides and related heterocycles”, Springer Verlag (1987). The synthesis of one such polymer is specified below.

Synthesis of poly(Leu)₄₀poly(GluOMe)₈₀: 10 g of NCA-GluOMe are solubilized in 150 ml of NMP at 60° C. 5 ml of a solution of 0.91 g of benzylamine in 50 ml of NMP are added all at once to the monomer. After 1 h, 14.1 g of NCA-Leu, previously solubilized in 20 ml of NMP, are added. Polymerization continues for a further 3-4 h.

Sampling of the reaction medium affords the following characterizations: Yield: 90%. Composition by ¹H NMR (TFA-d): 66 mol % of GluOMe. Reduced viscosity (0.5% of TFA at 25° C.): 0.4 dl/g. Molecular weight by GPC: 20,000 g/mol.

Example 2 Aminolysis of Poly(Leucine/Methyl Glutamate) Block Copolymer with Hydroxyethylamine

10 g of hydroxyethylamine are added all at once to the NMP solution of polymer prepared according to Example 1. The medium is heated to 80° C. and kept at this temperature for 2 days. 150 ml of water are then added to the polymer solution, which is then purified by a dialysis step to ensure removal of the excess amine and the NMP. Finally, the particles are isolated by lyophilization.

Yield: quantitative. ¹H NMR (TFA-d): 8% of residual methoxy (3.5 ppm); 92% of hydroxyethylglutamine. Composition by ¹H NMR (TFA-d): 34% of Leu. Particle size (light scattering, QLS mode): 100 nm.

Example 3 Demonstration of Nanoparticles by Light Scattering (LS) and Transmission Electron Microscopy (TEM)

10 mg of particles of polymer 1 are suspended in 10 ml of water or an aqueous solution of salt. This solution is then introduced into a Coulter granulometer (or laser diffractometer). The results of particle size analysis of the different products tested are shown in Table 1 below. TABLE 1 Measurement of the size of the CP Example Polymer Size (nm) 2 poly[(Leu)_(0.66)]-poly[(Gln-N- 100 hydroxyethyl)_(0.37)]_(x) block copolymer

Example 4 Test of Association of Nanoparticles with a Protein (Insulin)

An isotonic phosphate buffer solution of pH 7.4 is used to prepare a solution of human insulin containing 1.4 mg/ml, corresponding to 40 IU/ml. 10 mg of the CP prepared in Example 1 are dispersed in 1 ml of this insulin solution. After 15 hours of incubation at room temperature, the insulin associated with the CP and the free insulin are separated by centrifugation (60,000 g, 1 hour) and ultrafiltration (filtration cut-off: 300,000 D). The free insulin recovered from the filtrate is assayed by HPLC or ELISA and the amount of associated insulin is deduced by difference. The amount of insulin associated with the CP is greater than 0.77 mg, representing more than 55% of the total insulin used.

The Table below collates the results of the measurements of degree of association performed on different CP. The degree of association expresses the percentage of associated insulin relative to the insulin used in a preparation containing 1.4 mg/ml of insulin and 10 mg/ml of CP. This value is converted to a loading factor which expresses a formulation with 100% protein binding, in mg of insulin per 100 mg of CP. TABLE 2 Measurement of the degree of association with insulin for a mixture of 0.14 mg INSULIN/mg CP Degree of Loading association factor Example Polymer (%) mg/100 mg CP 2 poly[(Leu)_(0.66)]-poly[(Gln- 99 13.6 N-hydroxyethyl)_(0.37)]_(x) block copolymer

Example 5 Pharmacokinetics and Pharmacodynamics of Insulin-Loaded CP in Fasted Healthy Dogs

The particle+insulin preparation of Example 4 was injected into dogs which had been rendered diabetic by total pancreatectomy and fasted since the previous evening. At 11 am the preparation was administered subcutaneously into the thorax at a dose of 0.5 IU of insulin per kg of live weight of the animal. The volume administered is between 0.18 and 0.24 ml. At the times −4, −2, 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44 and 48 hours, 1 ml of blood is taken by jugular puncture under vacuum into a sodium heparinate tube. 30 μl of whole blood are used immediately to measure the glycemia. The tube is then centrifuiged, the supernatant is decanted and the plasma is stored at −20° C. to assay the insulin. The results shown in FIG. 1 below show that the insulin is released up to 12 hours (solid line) and that there is a substantial hypoglycemic effect extending up to 20 hours (broken line) after injection. TABLE 3 Measurement of the duration of action of insulin (hypoglycemic effect) in the presence of CP according to the invention Time to return to Example Polymer basal level (h) soluble insulin (without CP) 1 2 poly[(Leu)_(0.66)]-poly[(Gln-N- 20 hydroxyethyl)_(0.37)]_(x) block copolymer

This Example demonstrates the non-denaturation of insulin in the presence of CP according to the invention.

Also, Example 2 makes it possible to demonstrate the increase in the duration of action of insulin compared with non-formulated insulin, and hence the usefulness of the CP as a delaying system for the controlled release of insulin. It also shows how it is possible to control the duration of action by the appropriate choice of hydrophobic group.

Example 6 Aminolysis of Poly(Phenylalanine/Methyl Glutamate) Block Copolymer with Hydroxyethylamine

10 g of hydroxyethylamine are added all at once to the NMP solution of polymer prepared according to Example 1 using the monomers NCA-GluOMe and NCA-phenylalanine. The medium is heated to 80° C. and kept at this temperature for 2 days. 150 ml of water are then added to the polymer solution, which is then purified by a dialysis step to ensure removal of the excess amine and the NMP. Finally, the particles are isolated by lyophilization.

Yield: quantitative. ¹H NMR (TFA-d): 6% of residual methoxy (3.5 ppm); 94% of hydroxyethylglutamine. Composition by ¹H NMR (TFA-d): 34% of Leu. Particle size (light scattering, QLS mode): 100 nm.

Example 7 Aminolysis of Poly(Leucine/Benzyl Glutamate) Block Copolymer with 3-aminopropylene-1,2-glycol

10 g of 3-aminopropylene-1,2-glycol are added all at once to the NMP solution of polymer prepared according to Example 1 using the monomers NCA-GluOBzl and NCA-Leu. The medium is heated at 80° C. for 2 days. 150 ml of water are then added to the polymer solution, which is then purified by a dialysis step to ensure removal of the excess amine and the solvent. Finally, the particles are isolated by lyophilization.

Yield: quantitative. Particle size (QLS, according to Example 3): 100 nm.

Example 8 Test of Association of Nanoparticles with a Protein (Insulin)

According to Example 4, the isolated particles of Example 6 and human insulin are used to give a loading factor expressed in mg of insulin per 100 mg of CP. Loading Degree of factor in Example Polymer association mg/100 mg CP 6 poly[(Phe)_(0.79)]-poly[(Gln- 99 8.5 N-dihydroxypropyl)_(0.21)]_(x) block copolymer 7 poly[(Leu)_(0.66)]-poly[(Gln- 99 13.7 N-dihydroxypropyl)_(0.33)]_(x) block copolymer 

1-20. (canceled)
 21. A method of preparing a copolymer that is a particle precursor, comprising: a) copolymerizing monomers of amino acid N-carboxy anhydrides (NCA) of at least types (i) and (ii), wherein: type (i) NCA monomers comprise NCA-Glu-OR CR (R=alkyl), NCA-Asp-OR (R=alkyl), NCA forms of hydrophilic neutral amino acids (NCA-AANI), or mixtures thereof, and type (ii) NCA monomers comprise NCA forms of hydrophobic neutral amino acids (NCA-AANO), wherein the copolymerization is in the presence of at least one non-aromatic polar solvent selected from the group consist of N-methylpyrrolidone (NMP)), dimethylformamide (DFM), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), pyrrolidone, and mixtures thereof; and b) precipitating the copolymer to obtain a particle precursor.
 22. A copolymer that is a particle precursor produced by the method of claim
 21. 23. The method of claim 21, whereby step a) further comprises copolymerization in the presence of at least one cosolvent selected from the group consisting of aprotic solvents, protic solvents, water, alcohols, and mixtures thereof.
 24. The method of claim 21, whereby the copolymer formed is a random copolymer with a molecular weight that is ≧2,000 Da.
 25. The method of claim 21, whereby the degree of polymerization is 30-600%.
 26. The method of claim 21, whereby the particle size of the copolymer is 0.01 to 0.5 μM.
 27. The method of claim 21, whereby the type (i) NCA monomers are NCA-Glu-OR and/or NCA-Asp-OR, and whereby the method further comprises an acid hydrolysis step comprising: c) contact the copolymer formed with an aqueous phase comprising at least one amine.
 28. The method of claim 27, whereby said step c) is carried out with water and at least one mineral acid and/or at least one organic acid.
 29. The method of claim 28, whereby the mineral acid is hydrochloric acid.
 30. The method of claim 28, whereby the organic acid is selected from the group consisting of: trifluoroacetic acid (TFA), acetic acid, dichloroacetic acid, organosulfonic acids, and mixtures thereof.
 31. The method of claim 27, whereby the proportions of water to acid, as expressed in parts by water, is 60/1 to 2/1.
 32. The method of claim 27, further comprising the step of: d) dialyzing the reaction medium to obtain an aqueous suspension of submicron particles comprising the copolymer.
 33. The method of claim 32, further comprising the step of: e) concentrating the aqueous suspension by converting the hydrophilic part of the glutamate monomers to acid, thereby resulting in acidic amphiphilic polyamino acids intermediates that are insoluble in water.
 34. The method of claim 33, further comprising the step of: f) filtering, washing, and drying the acidic amphiphilic polyamino acids intermediates to thereby obtain a copolymer that is a particle precursor.
 35. A copolymer that is a particle precursor produced by the method of claim
 34. 36. The method of claim 21, whereby the NCA-pAAI is a NCA of O-alkylated gluatamic or aspartic acid.
 37. The method of claim 26, whereby the NCA-pAAI is selected from the group consisting of: NCA-Glu-O-Methyl, NCA-Glu-O-Ethyl, NCA-Glu-O-Benzyl, and mixtures thereof.
 38. The method of claim 21, whereby the copolymerization takes place between a temperature of 20 to 120° C., a atmospheric pressure and in the presence of an amine initiator. 